You mean by this tag?

<meta name="viewport" content="width=device-width, initial-scale=1, maximum-scale=1">

I imagine the only problem here is the maximum-scale parameter. Is that so, or are there other ones?

I haven't touched a frontend for a few years. It was the case that this tag was needed to display anything on mobile (and Google would all but delist you if you omitted it or used it incorrectly). I imagine things have improved. The optimist in me would like to think that the tag isn't even necessary anymore, but I can't trust that guy.

Yeah, I use this one:

    <meta name="viewport" content="width=device-width, initial-scale=1">

and "initial-scale" is only needed by Chrome Android AFAIK.

I never notice this. On Firefox mobile there is an option to always allow zooming and it works well. I agree with you though. Using such an option should not be needed.

The same option exists in Chrome and Chrome-likes such as Brave. You can find it in the Accessibility page in Settings.

There are limited situations where I as a user really do want pinch-to-zoom disabled. Primary example would be browser-based games. Depending on what gestures the game uses, I sometimes end up zooming accidentally on mobile, which is super annoying.

Id prefer a "lock zoom" button in the browser, but I understand that may not benefit someone who never opens a browser menu and just wants a website to work.

The problem with adding buttons is that you end up with a lot of buttons. Which is then a cause of people not opening browser menus.

Separately, it makes more sense to me for websites to set the default they think is best, and then let users override it. This can be done today in any browser with a bookmarklet.

(None of this is to excuse websites which abuse their power. I just don't think removing that power is the right solution, at least not here.)

Yet another reason why abusing a document format to make applications is a bad idea.